1. Technical Field
This invention is related to the field of integrated circuit implementation, and more particularly to the power management of coprocessors.
2. Description of the Related Art
Computing systems may include one or more systems-on-a-chip (SoC), which may integrate a number of different functions, such as, graphics processing, onto a single integrated circuit. With numerous functions included in a single integrated circuit, chip count may be kept low in mobile computing systems, such as tablets, for example, which may result in reduced assembly costs, and a smaller form factor for such mobile computing systems.
In some SoC designs, processors included in the SoC may enter an inactive state upon completing certain computing tasks to reduce power consumption or to reduce the emission of electromagnetic interference (EMI). Coprocessors coupled to processors may similarly enter idle states to further conserve system power consumption or reduce EMI.
A voltage regulator may be used, in various SoCs, to maintain the voltage level of the power supply used throughout the SoC to prevent the voltage level from rising to a level, which may damage the circuits. Some voltage regulating systems may be capable of providing multiple voltage levels and outputs such that more than one power domain (i.e., one or more circuits coupled to the same supply voltage) may be created. Different functional blocks within the SoC may be connected to one of the multiple power domains, allowing for voltage levels across the SoC to be adjusted to match the requirement for the circuits in a particular power domain. For example, analog circuits, such as digital-to-analog converters, may be connected to an analog voltage domain to keep a steady voltage on these circuits while other voltage domains may vary voltage for power savings.
One issue with placing processors and coprocessors into low power or power-down modes is that such modes may create a delay when the circuits return to normal operation (also referred to herein as “waking up” or being “woke up”) to resume execution. In some low power modes, a voltage level may be maintained that is sufficient to preserve the state of the circuits such that resuming operation may only require enough time for the power supply voltage level to rise back to a full operational level. Other power modes, such as a full power-down mode, may not preserve the state of the circuits and resuming operation may require enough time for the voltage supply to rise back to a full operational level and may require additional time for the circuits coming out of this mode to be re-initialized or configured for the next task the circuits are to perform.